Qualidade fisiológica de sementes de Samanea tubulosa (Benth.) Barneby & J.W. Grimes sob diferentes condições térmicas

Abstract

The conservation and sustainable management of native forest species are essential for maintaining biodiversity and restoring degraded areas in Brazil. Considering the potential of the species for the rehabilitation of degraded environments, this study aimed to evaluate the influence of different temperatures on seed germination and early seedling growth of Samanea tubulosa (Benth) Barneby & J. W. Grimes. The experiment was conducted at the Forest Seed Laboratory of the State University of Maranhão, using seeds collected from the protection zone of the Estreito hydroelectric power plant reservoir in Maranhão, Brazil. Seed dormancy was overcome by scarification followed by disinfestation. The germination test was carried out in a completely randomized design, with four replications of 25 seeds, under temperatures of 25°C, 30°C, 35°C, 40°C, and 45°C in B.O.D. chambers with a 12-hour photoperiod. Germinative, morphological, and physiological parameters were evaluated. The results showed that germination was faster and more uniform between 30 and 35°C. Early growth was also favored under these conditions. At 40 °C, a significant reduction in seedling development was observed, and at 45 °C the effects were even more pronounced, with a severe decrease in germination speed and growth. The analysis of photosynthetic pigments indicated higher concentrations of chlorophyll a and carotenoids at 35 °C, with a marked reduction at 40 °C. S. tubulosa demonstrated broad thermal tolerance, with greater germination vigor, initial growth, and pigment synthesis between 30 and 35 °C. However, from 40 °C onward, there was a sharp decline in physiological performance, indicating a stress threshold